The wavelength of light from the spectral emission line of sodium is 589 nm. Find the kinetic energy at which
(i) an electron, and
(ii) a neutron, would have the same de-Broglie wavelength .

Explanation

To solve the problem, we need to find the kinetic energy at which an electron and a neutron would have the same de-Broglie wavelength of 589 nm. We will use the de-Broglie wavelength formula and rearrange it to find the kinetic energy.

### Step-by-Step Solution

**Step 1: Understand the de-Broglie Wavelength Formula**

The de-Broglie wavelength (\( \lambda \)) is given by the formula:
\[
...